The invention relates to a composite film, a method for producing a composite film as well as a method for producing a film composite consisting of at least one composite film. The invention further relates to an apparatus for producing a composite film.
A composite film of this kind is particularly known from the food or nutriment industry and hereby serves to produce packaging which in each case contains a certain quantity of food or nutriments. Such composite films are particularly known in the production of so-called tubular bag packages. Such tubular bag packages are produced by two opposing peripheral regions of a composite film, or even two separate composite films, being laid against each another, wherein the peripheral regions on the sealing layers of the composite film, which are laid against each other, weld with one another while being subjected to heat and pressure. The composite films thereby consist of a plurality of layers which are connected to one another and have different melting points. During the sealing process, the film layers having the lowest melting point melt initially. It is therefore customary when welding composite films on the inner side of the package for those layers having the lowest melting point to be disposed as the sealing layers.
Due to economic considerations, a sealing layer, which simultaneously forms the inner layer of the packaging is in this case worth considering, in particular polyethylene (PE). Other plastics having a higher melting point with respect to PE as, for example, polyamide (PA) or polyethylene terephthalate (PET), are not used as the sealing layer because these polymers have too high a melting point so that they can not be economically welded in the packaging field or the strength of the weld seam is not sufficient. In addition, the use of such plastics as PA or PET on the inner side of the package is not possible when plastics having a lower melting point in comparison thereto are simultaneously used. This is the case because the layer having the lower melting point would initially melt without melting of the layer on the inside of the package having the higher melting point in relation to the aforementioned layer occurring.
It should be additionally mentioned that the use of polyethylene (PE) in particular as the innermost packaging material layer, which in turn has contact with a bulk material, is not suitable as packaging for sensitive food as, for example, mineral water, due to the high migration capability thereof.